The present invention relates to apparatus for testing IC devices for performance at a low temperature and to cooling bags for use as cooling means in testing IC devices at a low temperature.
So-called IC handlers are already known as apparatuses for testing IC devices for performance at a predetermined temperature condition using an IC tester. However, these apparatuses are usable only for testing at room temperature or high temperatures, so that when IC devices are to be tested at a low temperature, the IC device is placed on the head of the IC tester with an iron plate interposed therebetween, and liquid nitrogen or like refrigerant is applied to the device.
This method nevertheless has the following drawbacks.
(a) The water vapor in air condenses on or frosts the cooled IC device cause to short-circuit the device.
(b) The method encounters difficulties in controlling the temperature because of marked changes in temperature and further because it is difficult to accurately detect the temperature with a temperature sensor, hence inaccurate test results. The method is not amenable to a continuous operation since the operation needs to be interrupted frequently for the adjustment of temperature.
(c) The IC device has surface irregularities, and the surface of the IC device differs in cooling condition from portion to portion according to the direction in which the refrigerant is applied, so that it is difficult to cool the device uniformly in its entirety. Consequently, uneven cooling locally produces thermal stress (thermal expansion or contraction) to cause damage to the device.